1. Field of the Invention
The present invention relates to a resistance change memory having a resistance change element, and a write method of the resistance change memory.
2. Description of the Related Art
An MRAM (Magnetoresistive Random Access Memory) using a magnetoresistive element, a PRAM (Phase-change Random Access Memory) using a chalcogenide element, an ReRAM (Resistance Random Access Memory) using a transition metal oxide element, and the like are known as resistance change memories using resistance change elements. The feature of these resistance change memories is that information is stored by using the change in resistance value.
In a spin transfer torque magnetization switching type MRAM, magnetization in a magnetization free layer is inverted by spin transfer torque in accordance with the direction of an electric current supplied to the magnetoresistive element, thereby controlling the resistance value of the element (e.g., patent reference 1). In the PRAM, the phase is changed to a crystalline state or amorphous state by controlling the process from heating to cooling in accordance with the magnitude and the shape such as the width of a current/voltage pulse applied to the chalcogenide element, thereby controlling the resistance value of the element (e.g., patent reference 2 and non-patent reference 1). The resistance value of the transition metal oxide element of a bipolar ReRAM is controlled in accordance with the direction of a current/voltage pulse applied to the element, and that of the transition metal oxide element of a unipolar ReRAM is controlled in accordance with the magnitude and the shape such as the width of a current/voltage pulse applied to the element (e.g., non-patent reference 2). These resistance change memories thus write information in the resistance change elements.
To read out information stored in the resistance change element of any of the resistance change memories described above, a read current is supplied to the resistance change element, and the resistance value is converted into a current value or voltage value. The resistance state is determined by comparing this current value or voltage value with a reference value.
In the resistance change memories as described above, care should be taken so that the write current or voltage after the resistance has changed has no effect, e.g., causes no write error on the state of the resistance change element in data write.    [Patent reference 1] U.S. Pat. No. 5,695,864    [Patent reference 2] Jpn. Pat. Appln. KOKAI Publication No. 2006-324501    [Non-patent reference 1] Woo Yeong Cho et al., “A 0.18-μm 3.0-V 64-Mb Nonvolatile Phase-Transition Random Access Memory (PRAM)”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 40, NO. 1, JANUARY 2005    [Non-patent reference 2] November 2007 NIKKEI MICRODEVICES P97-99